Assessing the effectiveness of artificial intelligence (AI) in prioritising CT head interpretation: study protocol for a stepped-wedge cluster randomised trial (ACCEPT-AI) od Vimalesvaran, K, Robert, D, Kumar, S, Kumar, A, Narbone, M, Dharmadhikari, R, Harrison, M, Ather, S, Novak, A, Grzeda, M, Gooch, J, Woznitza, N, Hall, M, Shuaib, H, Lowe, DJ